Accumulator



K. C. MARD June 21, 1960 ACCUMULATOR Filed Deo. 31, 1956 is I KENNET'VNJ E* /M AGEN ACCUMULATOR Kenneth C. Mard, Stratford,

Aircraft Corporation, ration of Delaware Filed Dec. 31, 1956, Ser. No. 631,562

8 Claims. (Cl. 13S-'30) Conn., assignor to United East Hartford, Conn., a corpo- This invention relates to an accumulator and to a braking system and is shown in connection with an aircraft rotor brake system.

An object of this invention is to provide a brake system which will stop the rotor head of a helicopter from turning, when necessary, in which the deceleration is limited.

Another object of this invention is to provide a rotor brake system having an accumulator which can be left in a locked position.

A further object of this invention is to provide a rotor brake system in which an accumulator provides for thermal expansion and contraction between changing temperatures preventing the releasing of the brake at low temperatures.

Another object of this invention is to provide an accumulator which is not dependent on air pressure.

A further object of this invention is to provide an accumulator having no moving seals.

Another object of this invention is to provide an accumulator which is preloaded mechanically.

A further object of this invention is to provide an accumulator which is preloaded in a manner deforming the rubber to the same slope as it would have if it were subjected to a predetermined pressure.

Another object of this invention is to provide an accumulator which will accept a prescribed amount of uid while maintaining the pressure on the fluid at a value within a predetermined minimum and maximum.

Other objects and advantages will be apparent from the specification and from the accompanying drawings which illustrate the invention.

Fig. 1 is a side elevational view of a helicopter showing the invention in a schematic fform as applied to the drive shaft of the rotor.

Fig. 2 is a sectional View of the accumulator used in the rotor brake system when it is subjected to a pressure under the designated preload pressure.

Fig. 3 is a sectional view of the accumulator used in the rotor brake system when it is subjected to a pressure greater than the designated preload pressure.

Fig. 4 is a top view of Fig. 2.

While Fig. l shows the silhouette of a specific helicopter, it is to be understood that the rotor shaft brake system can be used on any type of helicopter or on any rotating shaft. Further, referring to Fig. 1, a helicopter is shown having a body 2 which generally houses the pilot or cargo compartments and engine compartment. It is shown having a main rotor 4 with blades 6 attached thereto being ymounted for rotation on a drive shaft 8. A pylon 12 extends upwardly from tail cone 10. A tail rotor 14 is mounted on said pylon. This helicopter may be controlled by any control mechanism desired, such a control mechanism being shown in the patent to Alex, United States Patent No. 2,720,271.

The rotor brake system consists of three main parts: (1) the rotor brake 16 which engages the shaft 8, (2) the actuating mechanism 18 which is ,connected to the brake 16 by fluid line 20 and provides the force for operating said brake, and (3) an accumulator 22 which is connected to the uid yline 20 by a uid line 24.

atent 'i 2,941,549 Patented .lune 21, 1969 ice The rotor brake 16 can be of any uid operated type in which a band, pads or shoes 26 are positioned around a rotor shaft, or member connected thereto, for frictional engagement therewith to prevent or oppose rotation. A brake of this type is shown in the application to Tolomeo et al., Application Serial No. 491,886, no'w Patent No. 2,880,810, led March 3, 1955, for a Blade Positioner.

The actuating mechanism 18 comprises a cylinder and piston unit 28 having a piston 3l) slidably mounted within a cylinder 32. One end of said cylinder 32 is connected to the rotor brake 16 by a uid line or conduit 20 to actuate the means 26. The piston 30 has a piston rod 34 fixed thereto which extends through the other end of said cylinder. An actuating lever 36, which is pivoted at 38, has a connection with the piston rod 34 at 40 which permits movement of the piston 30 upon movement of the lever 36. The actuating lever 36 can be moved between an on and off position. This lever may be locked in either position by any means desired. While a hand actuated mechanism has been shown, any suitable type of actuating mechanism can be used.

An accumulator 22 is connected in the rotor brake system shown to the uid line 20 by a uid line or conduit 24.

and (3) an end nut 46. The cushion assembly cornprises a cylindrical metal shell 48 having one end externally threaded with threads 50. The end of the shell having the external threads 50 is formed with an inwardly tapering face 52. A cylindrical rubber liller 54 is positioned in the cylindrical shell 48 with its outer cylindrical surface being iixedly adhered to the inner cylindrical surface of the shell 48. The filler may be adhered by any satisfactory means such as 'vulcanizing or bonding. The rubber filler 54 is shaped ori-ginally to conform to the dot and dash lines A andv B as shown in Fig. 2. The surface of the concave face of the filler 54 represented by the dot and dash line A is so formed to utilize the rubber more efficiently. The surface of the concave face extends from the outer circumferential edge of the filler where it is attached to the shell 48 to an apex at C. In the filler assembly shown, the distance from the top` edge of the rubber filler to the apex C is approximately one-half the length of the rubber filler S4 from its one outer circumferential end to the other. The curve shown in Fig. 2 by the dot and dash line A is shown as a parabola formed from the equation y=ller thickness a=thickness through filler at point C K=a constant which determines the slope of the parabolaportion of the filler 54. A tapered surface 60 is formed on the annular portion of the end cap to have a sealing engagement with the tapered `face 52 of the shell 48. A groove is formed in the surface 60 to receive an O-ring 62. A passageway 64 extends from one side of said hollow projection 58 to the other. The end of said passageway 64 on the inner side of said projection has a litting 66 to receive one end of the fluid line 24.

The accumulator 22 is made up of three main. parts: (l) a cushion assembly 42, (2) an end cap 44,

n annulai end nut 46 is formed having internal threads 68 which are .adapted to threadably engage threads 50 of the .metal shell 48. An inwardly projecting flange 70 on said nut 46 engages the outer edge of the annular member 56 of the end cap 44 on :the opposite side ,of .the projecting portion S. This `annular end nut 46 holds the accumulator 22 in its assembled position.

The hollow lprojection S8 extending from annular member 56 of Ithe end cap 44 has its outer surface formed so that, when it is forced into position as shown in Fig. 2, it mechanically .forms the rubber Vfiller to the same slope as it would .have if it were preloaded by some predetermined iluid pressure. This predetermined pressure provides the minimum pressure of the uid in the system at which the accumulator 22 will have an effect and Ithe projection reduces the amount of uid necessary for operation of the accumulator and rotor brake systern. This specific predetermined pressure (Pme) is a gure obtained `from the requirements of a specic brakin-g system and is placed at a value below the minimum pressure needed for proper brake operation. It can be seen that for a given volume of uid displaceable by piston 30, a higher pressure is obtained-with the projection S8 rather than a at plate. This permits the uid .to act more quickly on the brake in a proper manner.

For example, in a system such as shown in Fig. 1, the desired operating range of brake pressures (Pmn to Pmax) would be known along with the normal operating brake pressure (Pmrm). Further, for a given system, the amount .of fluid (Vb) .necessary to operate the brake at .this normal operating pressure, the amount of uid in the connecting'lines (V1), `and the amount of iluid (Vp) displaceable by the piston 30 from the cylinder 32 would .also be known. .Assuming that Ithe rotor brake system is going to be subjected to temperatures ranging between -65 F. and 160 F., the expansion of the fluid (Vex) in the system can be readily ligured between these temperatures. While the temperature range -65 F. to 160 F. has been used, it is to be understood that any `.operating range can tbe `used and the expansion of Huid and relative volumes calculated accordingly. From the data set forth above, using safety factors, the amounts of `iluid .the accumulator will have to accept for proper operation can be figured.

The tiller is then formed of such a shape and has a durometer reading so that .in operation it will accept a predescribed amount of fluid due to change in volume of fluid and maintain a pressure in the system Within the range Pmm to PMX. It can be seen that it is necessary for the volume of the fluid .displaceable yby piston 30 to be greater than the volume of lfluid accepted by the brake for proper operation plus a small volume of fluid reacting with the filler at 65 F.l Y

In operation, when it is necessary to brake the drive shaft 8 of a helicopter, the actuating lever 36 Ais moved to its on position. If it is desired for Ythe brake to remain on, it is locked Vin this position. As the actuating lever 36 is moved `to its on position, it `moves a piston 30 which displaces fluid from a cylinder 32 which is moved through tluid lines 2t) and 24 to` the brake 16 and accumulator 22 respectively. The fluid is forced `into -the brake'l-G until the iuid 'pressure in the system has reached a predetermined pressure at which the accumulator has been preloaded. At this point fluid ows intoV the accumulator raising thepressure in the entire system until .the lever 36 has reached its full on position. When locked in this position, fluid volume changes in .the system `will not .affect .the brake operation since, as stated hereinbefore, the accumulator maintains the brake operating pressure bet-ween a. desired operating range.

It is to be understood that the invention is not limited to the .specific embodiment herein illustrated and described, but may be used inv other ways without departure from its spirit as defined in -the following claims.

I claim:

1. An accumulator comprising a hollow member, a

resilient solid iiller xed in said member, and end cap fixed to one end of said member, a projection extending away from said end cap towards said ller and preloading it, and a passageway extending through said end cap.

2. An accumulator comprising a cylinder, a resilient solid filler -xed in said cylinder, said ller having a concave end, an end cap fixed to one end of said cylinder forming a chamber with said concave end of said ller, a projection extending away from said end cap into said concave end of said iillerv and preloading it, and a passageway extending through said end cap to said chamber.

3. An .accumulator comprising a cylinder, a resilient ller Aixed in said cylinder, said ller having a concave end, an end cap fixed to one end of said cylinder lforming a chamber with said concave end of said filler, a projection extending away from said end cap vinto said concave end of said filler and preloading it, and a passageway extending through said end ycap to said chamber, said projection deforming said filler so that it `assumes the shape it would `at some fluid pressure.

4. An accumulator comprising a hollow member having an inner surface, a resilient ller having an outer surface, said outer surface of said resilient lfiller being f xed to the inner surface of said hollow member, an end cap xed to one end of said member, a projection extending from said end cap towards said ller and preloading it, land a passageway extending through said end cap. 4 l j 5. An accumulator comprising a cylinder having an inner surface, a resilient filler having an outer cylindrical surface, said outer cylindrical surface of said liller being substantially equal to the inner surface of said cylinder, said outer surface of said -iiller being fixed to the inner surface o'f said cylinder, said filler having Va concave end, an end cap xed to one end of said cylinder forming a chamber with said concave end of said ller, a projection extending from said .end cap into said concave end of said filler preloading it, and a passageway extending through said end cap to said chamber.

6. An accumulator comprising a hollow member, a resilient ller fixed in said member, said ller occupying a substantial portion of the space within said hollow member, an end cap fixed .to one -endl of said member, a projection extending away from said end cap towards said filler and preloading it, and a passageway extendingV through said end cap. i

7..An accumulator comprising a cylinder, Ya resilient filler tixed in said cylinder, said ller occupying a substantial portion o'f the space within said cylinder, .an end cap xed to one end of said cylinder, .a projection extending away from said end .cap towards one end of said Vfiller and preloading it, said other 'end 0f said llerbeing free to move, and a vpassageway extending through said end cap.

8. An accumulator comprising a cylinder having an inner surface, -a .resilient iiiler having an outer surface, said outer surface of said lresilient -ller being fixed to the inner surface of said cylinder, an end cap fixed to one end of-said cylinder, a projection extending from said end cap towards one end of said fliller and preloading it, said other end of said filler being open to atmosphere,` and a passageway extending through said end cap.

References Cited in the .tile of this patent j UNITED STATES PATENTS 

